There's a thread on Jetcareers authored by a fellow who recently started down the path at AllATPs. Maybe you would find his commentary useful.
I did several ratings at AllATPs and found the quality of instruction was good and had no complaints. All four of the instructors I dealt with CFI'd until they had their 1500 hours and then left for the regionals. If they hated their time there they did a good job of keeping it to themselves.
I also did a rating at Aerosim in Sanford, FL, and it was a slow and drawn out process. I don't think I would enjoy instructing there.
My guess is that some AllATP locations are better than others.